Then drain water from the urad dal and keep the water aside for sprinkle while grinding.Sprinkle water in between at regular intervals and grind it for 40 minutes.first grind urad dal and collect it in a container after correct soft fluffy consistency.
Then drain water from the rice and grind it.Rice batter is little thicker than the urad dal batter.

take both rice batter and urad dal ,add salt and mix well in a big container.Keep the container in a warm place for ferment for atleast 12 hours(1/2 day).After 12 hours the batter will raised and come to the top of the container.